docs: def _get_model_fitting(self, mf_id):
          """
          Retreive model fitting with identifier 'mf_id' from the list of model
          fitting objects stored in self.model_fitting
          """
          for model_fitting in self.model_fittings:
              if model_fitting.activity.id == mf_id:
                  return model_fitting
  
          raise Exception("Model fitting activity with id: " + str(mf_id) +
                          " not found.")